Relative sea level rise issues and vulnerability in the Mediterranean basin: state of the art on the methodological aspects and assessment of their suitability

The rising sea level is considered one of the most evident consequences of ongoing climate warming. Similarly, the spatial distribution of weather and paroxysmal events in coastal areas, as well as their temporal occurrence, are being modified by climate change. Low-lying coastal areas and related mobile coastal systems (e.g., alluvial coastal plains, sandy beaches, delta river mouths) are particularly prone to be affected by sea level variations (SLVs), both temporary (i.e., storm surge and tsunami – SS and Ts) and permanent (i.e., sea level rise - SLR), especially when combined with negative vertical land movements (VLMs). In recent years, the number of studies focusing on the analysis of potential coastal vulnerability to SLVs that consider the local geomorphological settings coupled with the expected SLR has constantly increased. In this study, an analysis of the peer-reviewed papers addressing the sea level rise issues is performed through the evaluation of documents included in a database implemented by searching in Scopus through specific research queries. Special focus is given to the methodological aspects proposed to evaluate SLR impacts on coastal systems of the Mediterranean region. Then, a sub-set of papers published in the last five years was selected, reviewed, and categorized according to the methods applied for the sea level impact evaluation. Finally, the evaluation of the suitability level of the methods applied in the select papers is also proposed, expressing the level of applicability of each method in relation to specific aspects of analysis.

The results allowed  to state that on a global scale, since 2008 the number of peer-reviewed papers dealing with current sea level rise issues is constantly increasing, with the maximum published number reached in 2021 and 2023. Furthermore, a high number of papers are focused on the “tsunami” analysis and impact evaluation and, among the collected papers, more than 50% of them included in the title the words “SLR” and “Vulnerability”. Concerning the Mediterranean scale, the analysis has highlighted that a higher percentage of research papers (87%) was published in the period 2008-2023 and that the highest number of papers per year (14) was published in 2016 and 2021. Furthermore, Italy, Egypt, and Spain are the countries with the highest number of published papers. Finally, for what concerns the analysis of the methodological approaches, the GIS-based static method is still the most used in the papers published over the last 5 years, followed by model-based approaches. Nevertheless, the accuracy of the most recent studies can be considered higher due to the availability of i) more detailed projections of the future sea level derived from high-resolution models, ii) high-resolution digital terrain models, and iii) advanced satellite-derived data analysis for the assessment of accurate VGMs. Thus, although there has not been a clear shift in the applied methodological approaches, more recent works are based on the use of more accurate and defined input data. The modelling approaches are highly exploitable in the case of limited areas to be investigated, due to the high computational efforts required for the analysis.